1. Field of the Invention
This invention relates to the field of shock absorbers. Most particularly, this invention relates to a measuring a condition of a shock absorber based on temperature of shock absorbers.
2. Background
Shock absorbers are used on a wide variety of devices. Typically, one or more shock absorbers are mounted near each wheel of a vehicle. The shock absorber acts to translate kinetic energy from the wheel that is perpendicular to a road surface into thermal energy of a fluid of the shock absorber, thereby reducing or eliminating the perception of kinetic energy perpendicular to the road surface to the users of the vehicle. For example, if a wheel of a car hits a bump in a road, the kinetic energy perpendicular to the road surface that would be translated by hitting the bump into the passenger compartment of the car is partially or completely dampened by the fluid of the shock absorber(s) attached to the wheel. Thus, shock absorbers provide a safer and more comfortable ride for vehicle users.
FIG. 1 shows a cross-sectional view of a typical shock absorber 100. The body of shock absorber 100 is made up of an outer cylinder (a.k.a. reserve tube) 120 and an inner cylinder (a.k.a. pressure tube) 130.
Shock absorber 100 may be mounted to a vehicle (or other mechanical device) using upper mount 110 to connect shock absorber 100 to a frame of the vehicle and lower mount 112 to connect to an axle of the vehicle. Typically, the shock absorber 100 is mounted within a spring (not shown in FIG. 1) that is also connected to the frame and the axle of the vehicle. The upper mount 110 is connected to piston 140 via piston rod 142.
Shock absorber 100 uses fluid 150 to translate kinetic energy of a vehicle into thermal energy. When a wheel connected to the axle of the vehicle impacts a bump or other obstacle, part of the energy of the impact is transferred to piston 140 via upper mount 110 and piston rod 142. As piston 140 moves within inner cylinder 130, small amounts of fluid 150 are permitted to pass through orifices 144a and 144b of piston 140. As only small amounts of fluid 150 are permitted to pass through orifices 144a and 144b; fluid 150 is kept under high pressure. As piston 140 moves through highly pressurized fluid 150, up-and-down motion of piston 140 is slowed, which dampens the motion of the spring. The motion of piston 140 and pressurization may then increase the thermal energy of fluid 150.
Shock absorber 100 may be subject to failure when fluid 150 escapes from the shock absorber 100 or fails to circulate and/or if the piston 140 and/or piston rod 142 is subject to mechanical failure.